Mongodb聚合跳过和限制排序在分页中带来重复记录

Question

我有以下查询，首先对文档进行排序，然后跳过并限制 10 条记录，以下是我的查询:

db.getCollection('jobpostings').aggregate([
{"$match":{
    "expireDate":{"$gte": ISODate("2018-08-12T00:00:00.000Z")},
    "publishDate":{"$lt": ISODate("2018-08-13T00:00:00.000Z")},
    "isPublished":true,
    "isDrafted":false,
    "deletedAt":{"$eq":null},
    "deleted":false,
    "blocked":{"$exists":false}
}},
{"$lookup":{"from":"companies","localField":"company.id","foreignField":"_id","as":"companyDetails"}},
{"$match":{"companyDetails":{"$ne":[]}}},
{"$sort":{
    "isFeatured":-1,
    "refreshes.refreshAt":-1,
    "publishDate":-1
}},
{"$skip":0},
{"$limit":10},
{"$project":{
    "position":1,"summary":1,"company":1,"publishDate":1,
    "expireDate":{"$dateToString":{"format":"%Y-%m-%d","date":"$expireDate"}},
    "locations":1,"minimumEducation":1,"workType":1,"skills":1,"contractType":1,
    "isExtensible":1,"salary":1,"gender":1,"yearsOfExperience":1,"canApplyOnline":1,"number":1,
    "isFeatured":1,"viewsCount":1,
    "status":{"$cond":{
        "if":{"$and":[
            {"$lt":["$publishDate", ISODate("2018-08-13T00:00:00.000Z")]},
            {"$gt":["$publishDate", ISODate("2018-08-11T00:00:00.000Z")]}]},"then":"New",
        "else":{"$cond":{
            "if":{"$lt":["$publishDate",ISODate("2018-08-12T00:00:00.000Z")]},"then":"Old","else":"Future"}}}},
            "companyDetails.profilePic":1,"companyDetails.businessUnits":1,"companyDetails.totalRatingAverage":1,
            "expiringDuration":{"$floor":{"$divide":[{"$subtract":["$expireDate",ISODate("2018-08-12T00:00:00.000Z")]},
            86400000]}},
            "companyDetails.totalReviews":{"$size":{"$ifNull":[{"$let":{"vars":{
                "companyDetailOne":{"$arrayElemAt":["$companyDetails",0]}},"in":"$$companyDetailOne.reviews"}},[]]}}}}

])

如果我评论 skip and limit 以下是我的结果:

但以下是我在 skip = 0, limit = 10 时的结果:

现在将上面的结果与以下 skip=10, limit=10 的结果进行比较:突出显示的文档在第二页中重复 (skip=10, limit=10):

对于其他文档，其他页面中也存在同样的事情。

Answer 1

您排序所依据的三个字段似乎不是唯一的，因此在后续执行中顺序可能会有所不同。要解决此问题，您可以向 $sort 添加其他字段。由于 _id 始终是唯一的，因此它可能是一个很好的候选者。尝试:

{"$sort":{
    "isFeatured":-1,
    "refreshes.refreshAt":-1,
    "publishDate":-1,
    "_id": -1
}}